Carboxylation, of olefins with

In this chapter, we discuss theoretical studies of some selected transition metal-catalyzed reactions of carbon dioxide to illustrate how important concepts and insights can be derived as a result of these studies. These selected reactions include hydrogenation of CO2 with Hj, coupling reactions of COj and epoxides, reduction of CO2 with organoborons, carboxylation of olefins with COj, and hydrocarboxy-lation of olefins with CO2 and Hj. They are fundamentally important reactions of carbon dioxide and have been intensively investigated experimentally and theoretically. This chapter is not intended to be a comprehensive review. Instead, we discuss the above-mentioned selected examples that we believe to be representative and important in the area of homogeneous catalysis of COj by transition metals from our own perspective. 

In this chapter, we have reviewed theoretical studies of selected transition metal-catalyzed transformation of CO2 (i) hydrogenation of CO2 with H2 (ii) coupling reactions of CO2 and epoxides (iii) reduction of CO2 with organoborons (iv) carboxylation of olefins with CO2 and (v) hydrocarboxylation of olefins with CO ... 

Figure 11 Scope and limitations of base (A) and substrate (B) for the catalytic one-pot carboxylation of olefins with CO2.

Huguet N, Jevtovikj I, Gordillo A, et al. Nickel-catalyzed direct carboxylation of olefins with CO2 one-pot synthesis of a, -unsaturated carboxyhc acid salts. Chem Eur J. 2014 20 16858-16862. 

Scheme 1.13 Oxidative carboxylation of olefins with homogeneous and heterogeneous catalysts.

If cobalt carbonylpyridine catalyst systems are used, the formation of unbranched carboxylic acids is strongly favored not only by reaction of a-olefins but also by reaction of olefins with internal double bonds ( contrathermo-dynamic double-bond isomerization) [59]. The cobalt carbonylpyridine catalyst of the hydrocarboxylation reaction resembles the cobalt carbonyl-terf-phos-phine catalysts of the hydroformylation reaction. The reactivity of the cobalt-pyridine system in the hydrocarboxylation reaction is remarkable higher than the cobalt-phosphine system in the hydroformylation reaction, especially in the case of olefins with internal double bonds. This reaction had not found an industrial application until now. 

Olefins react with manganese(III) acetate to give 7-lactones.824 The mechanism is probably free-radical, involving addition of CH2COOH to the double bond. Lactone formation has also been accomplished by treatment of olefins with lead tetraacetate,825 with a-bromo carboxylic acids in the presence of benzoyl peroxide as catalyst,826 and with dialkyl malonates and iron(III) perchlorate Fe(C104)3-9H20.827 Olefins can also be converted to 7-lactones by indirect routes.828 OS VII, 400. 

A study of the photoaddition of formamide to olefins was undertaken with the aim of finding a new process for converting olefins to higher amides and possibly further to amines by reduction or by the use of the Hofmann rearrangement. Since hydrolysis of the amides to the corresponding carboxylic acids can be effected by standard procedures, this reaction provides a new process for carboxylation of olefins under mild conditions at room temperature. A similar reaction has been shown to take place in a thermal process, using peroxides as initiators (60). 

The palladium(II)-mediated oxidative coupling of olefins with oxygen-nucleophiles (ROH water, alcohols, carboxylic acids) is a stoichiometric reaction with respect to Pd(II), resulting in an oxygenated product and Pd(0). To convert Pd(0) back to Pd(II) and start a new reaction cycle, a reoxidation reaction (which can itself be stoichiometric or catalytic) using a terminal oxidant is required. In this way, the overall process becomes catalytic with respect to the expensive Pd salt. 

Oxyselenation ofalkeues, - Treatment of olefins with 1 or 2, water, and an acid catalyst (e.g., p-TsOH) in CH2CI2 affords j3-hydroxy selenides in excellent yield. Unsaturated carboxylic acids, phenols, alcohols, thioacetates, and urethanes react with 1 or 2 and an acid catalyst ( —78- 25°) to afford products of oxidative cyclization. These reagents are superior to benzeneselenenyl halides for selenium-induced ring closures. This reaction is also useful for synthesis of 14- and 16-membered lactones. Benzeneselenenyl halides and benzeneselenenic acid do not promote macrolide formation under similar conditions. 

Koch-Haaf earboxylation This acid is much superior to the previously used 95 % H2SO4 for carboxylation of olefins, alcohols, and esters with CO at atmospheric pressure. The beneficial effect appears to be the higher solubility ol CO in this acid. 

The Ni-catalyzed electrocarboxylation of differently activated olefins has been reported to afford selective CO2 incorporation via hydrocarboxylation [11]. However, no CO2 incorporation occurred with non-activated alkenes such as 1- or 4-octene. Carboxylation of olefins 3 and 4 should give some indication on the influence of the Rp substituent on the double bond. 

PhjSbO mediates the dehydrative condensation of carboxylic acids with amines via Ph3Sb(OCOR)2 as reactive intermediates [146]. This catalytic system has been applied to dipeptide synthesis (Scheme 14.73) [147]. Treatment of olefins with a mixture of AcOH and P4S10 in the presence of Ph jSbO affords alkylthio esters [148]. 

Acyclic carboxylic acids from single or mixed hydrocarbons of known constitution this includes reaction of acetylene with CO and water, reaction of olefin with CO and water, and also dibasic acids from cycloalkanes... 

Additions to multiple bonds catalyzed by radical initiators produce novel synthetic methods. Carboxylic acids add to acetylenic compounds in the presence of organic peroxides. Acetic acid and acetylene yield adipic acid 1-hexyne and acetic acid give octen-3-oic acid. Radical amination of olefins with hydroxylamine sulfonic acid and hydroxylamine in the presence of FeCla gives the corresponding l-amino-2-chloro compounds. ... 

Although the formation of three-membered rings by cyclopropanation of olefins with metal carbenoids is commonplace, the construction of such systems via intramolecular C-H insertion is quite rare. This is because 1,2 migration of any hydride atoms a to the carbenoid center is typically very facile, rendering it inactive toward further transformations [56], It was found, however, that [i-tosyl a-diazo carbonyl compounds 37 are suitable substrates for intramolecular 1,3 C-H insertion reactions catalyzed by achiral rhodium carboxylates 25 (Scheme 6) [57],... 

Phosphates and phosphinates are also recommended as ligands. (R)- or (S)-Binaphthol phosphates 3.54 are used in palladium-catalyzed asymmetric hydro-carboxylation of olefins [923] or in rhodium-catalyzed cycloadditions of diazo compounds to olefins, albeit with modest selectivities in the latter case [924], Seebach and coworkers [925] tested phosphinates and phosphites prepared from diol 2.50 (R = R = Me, Ar = Ph) as ligands for rhodium and palladium in various enantioselective metal-catalyzed reactions [925], Rhodium-catalyzed hydrosilyla-tions of arylmethyl- or ethylketones by Ph2SiH2 were the only interesting reactions with these ligands. 

Mark and Rechnitz [3] systematized a vast amount of experimental material that can be used directly in KGCM. Some data are presented here that show the wide differences in organic compounds with regard to their kinetic characteristics. Table 2.1 [14] gives the relative rates of reaction of olefins with perbenzoic acid and Table 2.2 summarizes the rates of the etherification reaction of carboxylic acids with diphenyldiazomethane [15]. The tabulated data are indicative of large differences in organic compounds as far as their reactivity is concerned. The rates of reaction of some isomers differ so widely that one can, for example, analyse secondary and tertiary alkyl bromides in the presence of primary alkyl bromides in a reaction with silver nitrate [16]. It is possible to differentiate between CIS and trans isomers of 1,3-dienes by their reaction with dienophils (e.g., chloromethylene anhydride) because the cis isomer reacts much more slowly than the trans isomer [17]. 

This is actually a crucial step in the carboxylation of olefins (Reppe reaction) with transition metal carbonyl catalysts Apart from these extreme cases, however, metal-carbon a-bonds as well as metal-hydride bonds are best described as moderately polarized covalent bonds, with negative charge on the carbon or hydrogen respectively ... 

The oxidations of olefins with many oxygen nucleophiles other than water have also been reported. These reactions include the s5mthesis of vinylic and allylic ethers from reactions of olefins with alcohols and phenols, and vinylic and allylic esters from reactions of olefins with carboxylic acids. These reactions have been conducted with both monoenes and 1,3-dienes. Both intermolecular and intramolecular versions of each of these processes have been developed. Some discussion of these reactions was included in Chapter 11 because of their connection to the nucleophilic attack of oxygen nucleophiles on coordinated olefins and dienes. 

Intermolecular Additions of Alcohois and Carboxylates The intermolecular oxidations of olefins with alcohols as nucleophile typically generate ketals, whereas the palladium-catalyzed oxidations of olefins with carboxylic acids as nucleophile generates vinylic or allylic carboxylates. As a result, many of the oxidations with alcohols have been conducted with diols to generate stable cyclic acetal products. Both types of oxidations have been conducted on large industrial scale, and vinyl acetate is produced from the oxidative reaction of ethylene with acetic acid in the gas phase over a supported palladium catalyst. ... 

Examples of the oxidative reactions of olefins with carboxylic acids are shown in Equations 16.107-16.109. These examples illustrate the selectivities of the oxidations of ethylene, acylic alkenes, and cyclic alkenes. The reactions of alkenes with carboxylic adds generate either vinylic esters or allylic esters. 

The third and fourth examples involve intramolecular oxidation of olefins with a protected alcohol and with a carboxylic acid. Cleavage of a silyl protected alcohol, followed by oxidative C-0 bond formation at the p-position of an acrylate group was conducted at the late stage of the synthesis of the alkaloid alstophylline. Intramolecular 1,4-oxidations of dienes have been used in the synthesis of a number of natural products. For example, the intramolecular oxidation shown in Scheme 16.30 led to the precursor to Paeonilactone... 

Reaction time has to be as short as possible in order to suppress side reactions. Especially the conversion of alcohols to carboxylic acids with one more C-atom, which will be discussed subsequently, or formation of ethers and free acids may be undesirable reactions [504]. The carbonylation rate of olefins with carbon monoxide/ROH in the presence of Co carbonyls can be accelerated remarkably by addition of small portions of hydrogen to carbon monoxide, which favors the formation of hydrocarbonyl. The same effect can be achieved by addition of pyridine. 

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